By Tim Turney

In terms of public perception of health and safety hazards in the workplace, arguably few are as well known as the risks associated with asbestos. Until the 1970s, “asbestos” was a word synonymous with safety, and the mineral was used in the automobile, construction, power, and chemical sectors, among others, as part of the industries’ fireproofing measures. But once legislation was implemented to control asbestos exposure and word spread about the severe health effects it can cause, including mesothelioma and asbestosis, asbestos became one of the most high-profile health and safety considerations worldwide. This is inarguably by necessity: approximately 90,000 people die from asbestos-related illnesses globally each year, making it the number-one cause of work-related deaths in the world. And just as perceptions of asbestos shifted as its impacts on health came to light, we are now seeing a similar shift regarding a substance that many are hailing as “the next asbestos”—crystalline silica.

Many individuals’ understanding of silica might be limited to the small packets found in some home shopping deliveries, but in industrial sectors silica is so present that it is impossible to avoid. Silica, the second most abundant mineral in the world, is found in varying amounts in most rocks, sand, and clay, and is a major constituent in construction materials made from these resources, including bricks, tiles, and concrete. Silica itself is not the main cause for concern; instead, it’s the inhalation of silica in its crystalline form, which occurs naturally in varying amounts in any substance containing silica, that poses potential health concerns. Due to the ubiquity of materials containing silica in industry, approximately two million U.S. workers face ongoing exposure to risks from crystalline silica. These factors should be sobering, especially when considered alongside the fact that conditions caused by inhaling crystalline silica, such as silicosis, are debilitating and irreversible.

As with any known workplace health risk, a correctly implemented scheme of controls and procedures is the most effective means of reducing worker exposure to respirable crystalline silica. This can help reduce both the likelihood of workers developing health complications such as silicosis and the potential legal ramifications for employers. It is imperative that these controls include an efficient, correctly executed program of air monitoring, which can include both monitoring at the site level and on an individual employee level using personal sampling pumps.

Correct implementation of personal sampling relies on a thorough understanding of practice, procedure, and how sampling pumps function, especially when benchmarked against national and international performance standards. One such benchmark requires an understanding of how pumps operate, considering how pulsation can affect data capture results.

With every cycle of a sampling pump, air is drawn in and out in a similar way to how a worker in the same environment would breathe. The resulting airflow is not completely smooth and includes an alternating, or pulsating, component due to the pump’s internal movement. The impact that pulsation has on performance is expressed as the ratio of the pulsating component amplitude to the mean (steady) flow rate. As sampling heads, like cyclones, rely on a steady flow to maintain a specific size “cut,” it is important for pulsation to be as small as possible.

Pump pulsation is a known cause of measurement error within the industry, so much so that it is cited in the OSHA Technical Manual, which states that “tests with precision rotameters have indicated significant error due to pump pulsation.” This, in effect, precludes traditional “analog” calibration methods using rotameters from being used reliably, as they include a larger margin of error. According to research published in the January 2014 issue of the Annals of Occupational Hygiene, deviation from the specified airflow for a cyclone will result in the sampled air not accurately reflecting the respirable size fraction. In accordance with ISO 13137, airflow pulsation should not exceed 10 percent. Only one flow meter on the market at present can detect if pulsation exceeds this limit. With primary standard flow meters, it is impossible to see if pulsations are occurring. But with electronic flow meters that give instantaneous results, it may be possible to visually estimate if pulsation is above 10 percent.

The electronic flow meter represents a more contemporary innovation within airflow measurement technologies. As a diagnostic tool, electronic airflow meters allow for traceable measurement results, saving time and reducing the risk of errors compared to more traditional methods where results would be taken down manually. Electronic airflow meters also deliver better accuracy, testing to 1–2% greater accuracy than systems such as rotameters. When monitoring for particulate matter such as crystalline silica, which has such a high risk to health, and with so much current industry and public scrutiny surrounding it, there can be no margin for error, especially not one caused by something as avoidable as pulsation.

Personal sampling pumps must adhere to the standard ISO 13137:2013. The standard sets limits for required flow stability and maximum permissible pulsation levels, enabling users of personal air sampling pumps to adopt a consistent approach for flow rate assessment. The standard provides a comprehensive framework that specifies test methods to determine performance of air sampling pumps and ensures that environmental influences such as air pressure and temperature have a minimal impact on the accuracy of the sampled air, which in turn could affect sample results.

Correct equipment—calibrated properly—and an awareness of the limitations and impact on data collection that the equipment itself can have should be at the forefront of correct air monitoring procedures as well as the fight against “the new asbestos.” Pumps, including the Apex2, that operate with a pulsation value of less than 10 percent and conform to all relevant ISO standards give industrial hygienists and site managers the peace of mind that data captured is reliable and unaffected by pump pulsation.

While awareness of silica’s negative health effects is on the rise, correct procedure, safety-focused culture, and the right equipment will ensure that the downward trend in silicosis mortality continues.

Allianz eBroker: “How to Stop Silicosis Becoming the New Asbestos” (April 2018).

Asbestos.com: “Asbestos Facts & Statistics.”

Asbestos.com: “History of Asbestos.”

CDC: Morbidity and Mortality Weekly Report, “Silicosis Mortality Trends and New Exposures to Respirable Crystalline Silica — United States, 2001–2010” (February 2015).

Health and Safety Executive: “Cancer and Construction: Silica.”

International Organization for Standardization: ISO 13137:2013, Workplace Atmospheres — Pumps for Personal Sampling of Chemical and Biological Agents — Requirements and Test Methods (October 2013).

OSHA: OSHA Technical Manual, Section II: Chapter 1, Appendix F: Calibration.

SAMS Ltd: “Silica Dust Is the New Asbestos” (August 2018).

The Actuary: “Is Silica the New Asbestos?”